Heat exchange tubing



Feb. 20, 1962 w, ABBOTT 3,022,049

HEAT EXCHANGE TUBING Filed July 10. 1959 F'IG.2

INVENIOR ROY W. ABBOTT BY @X H l 5 ATTORNEY United States Patent-O 3,022,049 HEAT EXCHANGE TUBING Roy W. Abbott, Jefi'ersontown, Ky., assignor to General Electric Company, a corporation of New York Filed July 10, 1959, Ser. No. 826,241 2 Claims. (Cl. 257262.13)

been preformed along its length into a tube forming flange and an angularly disposed longitudinal fin portion. The fin portion is transversely slit from its outer edge toward the tube forming flange into a plurality of angularly disposed slender fin sections and the tube forming flange is provided with a plurality of longitudinal folds spaced apart an equal distance from each other and arranged parallel to the length of the flange. The strip is helically wound with successive laps or wraps of the tube forming flange overlapping and with the angularly disposed fin sections extending outwardly around the outer periphery thereof. The folds of the tube forming flange are so arranged that they nest or interlock to prevent axial movement of the overlapping portions of the flange. In order to seal the tubing and to secure the adjacent wraps of the tube forming flange together a bonding material is provided between the overlapping portions of the flanges.

For a better understanding of the invention,.reference may be had to the accompanying drawing in which:

FIG. 1 is an elevation view illustrating the helical fin and tube arranged of the present invention;

FIG. 2 is a partial cross-sectional view taken along line 22 of FIG. 1;. and J FIG. 3 is a partial cross-sectional view of the tubing taken along line 3-3 of FIG. 1.

Referring now to the drawing, there is shown a tubular structure adapted for heat exchange purposes such as for use in air conditioning apparatus or in refrigerating equipment. As shown inFlGS. l and 3, the structure comprises a base surface or tubing 2, which carries the cooling medium, and a secondary surface in the form of a plurality of slender fin sections 3, which radiate outwardly from the tubing. As is clearly shown in the cross-sectional view of FIG. 2, the fin sections and the tubing are formed of one and the same strip of material. More specifically, the structure comprises a continuous strip of sheet stock that is folded or formed into a tube forming flange 4 and an angularly disposed fin portion 3a. For ease of description the strip 5 of sheet stock is shown in the drawings to be much thicker than would ordinarily be used for tubing provided for use in refrigerant carrying apparatus. It is contemplated that the sheet stock be relatively thin and of a material having a high degree of ductility such as aluminum, copper or steel. The fin portion 3a of the strip 5 is serrated from its outer edge toward its junction point with the flange 4 to provide the individual fin sections 3 which spread apart at their outer edges, as is best seen in FIG. 3, when the strip 5 is helically wrapped into a tubular form.

In order to form the tubing, the strip 5 is spirally or helically wound upon itself with the tube forming flange 4 of succeeding wraps overlapping portions of the tube forming flange of preceding wraps. The tube forming flange 4 is provided with a plurality of spaced-apart longitudinal folds or corrugations which are arranged parallel to the length of the flange 4 and to the length of the 3,022,049 Patented Feb. 20, 1962 strip 5 of sheet stock. In the illustrated embodiment of the invention, there are shown three folds 6, 7 and 3 and is easily seated within the fold 7.

in the tube forming flange, but it should be noted that any number of folds could be provided as long as there are at least two. The folds 6, 7 and 8 interlock to prevent axial movement of the adjacent wraps with respect to eachother and cooperate to provide a very strong tubular structure. More specifically, the first fold 6, or fold closest to the fin section 3a, of each wrap fits within the fold 7, or second fold, of the next preceding wrap. The first fold 6 is made smaller than the second fold 7 In a similar manner, the second fold 7 of each wrap fits within the third fold 8 of the preceding wrap. The second fold 7 is, likewise, made smaller than the fold 8 so that it fits snugly within the fold 8 when the tubing is fabricated.

Still referring to FIG. 2, it can be seen that the folds 6, 7 and 8 are spaced apart an equal distance from each other. That is, the apexes 9 of the separate folds or corrugations are all spaced apart an equal distance x from each other in order to cause the folds to interlock or fit within one another. In addition, the distance x, which is the distance between adjacent folds, must necessarily be equal to the pitch between adjacent wraps and therefore determines the helical wrapping angle of the strip 5. In other words, the tubing must be formed by helically wrapping the strip 5 of sheet stock so that the pitch between adjacent wraps is equal to the distance x between the folds in the tube forming flange 4-.

' A bonding material 11, such as a brazing material or an adhesive bonding agent, holds the adjacent wraps of the tubing together and seals the air spaces between the wraps to provide a sealed tubing capable of conducting a highly pressurized fluid medium. The bonding material 11 entirely fills the spaces formed in the folds between adjacent wraps of the strip of sheet stock and creats a gas tight bond between the overlapping portions of the tube forming flange 4. The interlocking action of the folds enhances the seal beween the adjacent wraps of the tubing by literally squeezing the bonding agent between the mating folds and causing it to spread into all spaces between the overlapping portions of the tube forming flange 4.

The present invention provides a finned tubular structure in which the tubing itself and the fin section comprise a single, integral piece. The structure requires no bonding or soldering agent to connect the fin surfaces or sections to the tubing and thereby eliminates the barrier to the flow of heat from the tubing to the outwardly extending fin surfaces which inherently occurs in those types of heat exchange structures in which the fin surfaces must be attached to the tubing. For example, when heat is taken or removed from any suitable source, such as an air stream which is passed through the fin section 3, it is transferred directly from the fin to the wall or tube forming flange of the tubing. Since the bonding agent 11 is not in the direct heat flow path from the fin section 3 to the tubing, it does not present a barrier to the flow of heat through the structure. In addition, because of the construction of the tubing, the inner wall surface contains a helical ridge or corrugation which promotes a highly turbulent flow in the fluid medium flowing through the tubing. The refrigerant or heat exchange medium is forced to rotate as it flows through the tubing and the rotation imparted to the heat exchange medium by the helical folds greatly enhances the heat exchange characteristics of the tubing, especially, when it is used as an evaporator. For example, when cold liquid and gaseous refrigerant is passed through tubing, the centrifugal force created by the swirling or rotating refrigerant forces the heavier liquid refrigerant toward the walls of the tubing thereby wetting the walls entirely around the periphery'thereof. By forcing the colder liquid refrigerant into contact with all of the inner wall surface of the tubing, the heat transfer through the tubing is greatly improved. a v

A further feature which increases the heat transfer characteristics of the tubing of the present invention is the greatly increased inner surface area available for transfer of heat to and from the heat exchange medium flowing through the tubing. Because of the corrugations or folded configuration a greatly increased surface area is available for heat transfer purposes as compared to the normal type of heat exchange tubing having a comparatively flat l or smooth inner wall surface.

While in, accordance with the patent statutes there has been shown what at present is believed to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications 'may' be made therein without departing from the invention and it is, therefore, the aim of the appended claims to cover all such changes and modifications as falla within' the true spirit and scope of the invention.

What I claim asrnew and desire to secure by Letters; 1

Patent of the United States is:

1. A finned tubular structure adapted for heat exchange purposes comprising a thin strip of sheet stock folded along its length into a tube forming flange and an anguthereof a plurality of fin sections extending radially outward therefrom.

2. A finned tubular structure adapted for heat exchange purposes comprising a thin strip of sheet. stock folded along its length'into a tube forming flange'fand an angularly disposed longitudinal fin. portion, saidzlongitudinal portion being serrated from its outer edge toward said.

tube forming flange into. a plurality of slender fin sections, said tube forming flange having a first fold,.disposedtherein parallel to the length of said strip and second and third folds disposed parallel to said first fold between said first fold and the edge of said flange, all of said folds being spaced, equal distances apart and increasing in size from saidlfirst to said third fold respectively, said tube forming lariy disposed longitudinal fin portion, said longitudinal fin portion being serrated from its outer edge toward said said tube forming flange having a plurality 0E equallyspaced apart folds formed longitudinally therein'and ar ranged parallel to the length of said strip, said fold closest to said fin portion being smallest in size with said remaining folds progressively increasing in size, saidtube forming flange spirally wound into a tubular structure with subsequent wraps overlapping preceding wraps thereof said folds on said flange extending inwardly and said folds of said flange of subsequent Wraps fitting into inwardly ex:- tending folds on said flange of preceding wraps, said fin sections extending radially outwardly from said tubular structure, and adhesive bonding means between adjacent tube forming flange into a plurality of slender fin sections,

flange. spirally wound into a tubular structure with the finned sections extending outwardly therefrom, said first and second folds on said flange. of subsequent windings fitting into the second and third folds on said flange of preceding windings, said folds extending inwardly intosaid tubular structure, and adhesive bonding means between overlapping portions of said tube forming flange in said folds thereof for securing overlapping portions of saidtube forming flange together and sealing the spac'ebetween said overlapping portions of said tubeforming flange so that a sealed tubular structure is provided having integrally formed with the wall structure thereof a plurality of finsections. extending radially outward therefrom.

References Cited in the fileof this patent Germany Dec. 1'1, 1952 

